Question

Explain giving reasons for the following :
(a) Photoelectric current in a photocell increases with the increases in intensity of the incident radiation.
(b) The stopping potential `(V_0)` varries linearly with the frequency (v) of the incident radiation for a given photosenstive surface with the stop remaining the same for different surfaces.
(c) Maximum kinetic energy of the photoelectrons is independent of the intensity of incident radiation.

Answer 1

(a) For the radiation of frequency (greater than threshold frequency of metal )photoelectric current is directly proportional to the intensity of incident radiation. So the increase in intensity of incident radiation increases the photoelectric current.
(b) As, `eV_0=hv-phi_0 or V_0=(hv)/e-(phi_0)/e......(i)` so stopping potential `V_0` is directly proportional to frequency v. So the graph (i) is a st. line equation. Comparing it a straight line equation y=mx+C, we have slope of his line =h/e =a constant. So slope of `V_0` and v graph =h/e which is constant for all surfaces.
(c) Max `KE=eV_0=hv-phi_0`. It is independent of intensity of incident radiation till v is constant.